Role of surface substances in excitation of porous silicon photoluminescence

Photoluminescence (PL) and photoluminescence excitation (PLE) spectra studies as well as SIMS and FTIR methods were used for investigation of PL excitation mechanism of porous silicon (PS). It is shown that there are two types of PS PLE spectra, which consist of either two bands (visible and ultraviolet) or only ultraviolet one. The different dependencies of intensity of each PLE band upon anodization regimes as well as during aging and thermal treatment were observed. Two excitation channels have been shown to be present in PS. The visible PLE band at 300 K has been attributed to light absorption of some species on Si wire surface.